The present invention generally relates to a tool holder assembly for the support of a machine tool such as, for example, a reamer, a cutting tool or a cutter, and more particularly, to a tool holder assembly of a type having a cutting fluid supply circuit for pouring a cutting fluid therethrough onto a workpiece being machine-processed.
Numerous machine tools having a cutting fluid supply circuit defined therein are currently commercially available. When in use, the machine tool is mounted on a particular machine, for example, a lathe, with the cutting fluid supply circuit communicated with an external source of cutting fluid, and the machine process proceeds while the cutting fluid is poured onto the workpiece being machine-processed. The purpose of the use of the cutting fluid varies depending on the type of the cutting fluid used and, in most cases, an oil type cutting fluid is widely used for the purpose of concurrently lubricating and cooling the machine tool as well as the workpiece being machine-processed. In view of this, the machine tool having the cutting fluid supply circuit is generally considered advantageous and convenient in that, since the machine tool can readily be lubricated and cooled by the cutting fluid being poured through the cutting fluid supply circuit defined in the machine tool, not only can the workpiece being machine-processed be smoothly machined, but also the life time of the machine tool can be increased.
Since this type of machine tool is, when in use, mounted on a tool holder removably or permanently secured to a rotary spindle of a machine for rotation together therewith, the cutting fluid supply circuit defined in the machine tool must be communicated with a cutting fluid supply circuit defined in the tool holder in order for the cutting fluid from the external source thereof to be supplied to the cutting tool by way of the tool holder. Hitherto, two methods are employed for the supply of the cutting fluid from the external source thereof to the fluid supply circuit in the tool holder. One of them is to supply the cutting fluid to the fluid supply circuit in the tool holder through a fluid passage, defined in a stationary support member supporting the tool holder rotatably, by way of an annular passage defined at the interface between the rotatable tool holder and the stationary support member, and the other is to supply the cutting fluid to the fluid supply circuit in the tool holder directly through a fluid supply passage defined in the spindle.
However, in either of these conventional fluid supply methods, the pressure under which the cutting fluid flows from the external source towards the fluid supply circuit in the machine tool depends on, and is solely derived by, the discharge pressure of the pump forming a part of the external source of the cutting fluid. Accordingly, in the event of the occurrence of the loss of pressure during the supply of the cutting fluid from the pump towards the fluid supply circuit in the machine tool, either the insufficient pouring of the cutting fluid onto the workpiece being machine-processed, or the interruption of the fluid pouring, tends to take place. Therefore, according to any one of the above described conventional methods, for the stabilized supply of the cutting fluid under the constant pressure throughout the entire circuit from the cutting fluid source to the fluid supply circuit in the machine tool, the external fluid source is require to employ a relatively expensive and bulky pump capable of exerting a relatively high discharge pressure, the use of such a pump being susceptible to the leakage of the cutting fluid during the supply thereof from the pump towards the machine tool and also to the problem associated with the ecomony of the machine processing.
Specifically, in the method wherein the cutting fluid is supplied to the tool holder through the fluid passage, defined in the stationary support member, by way of the annular passage defined at the interface between the rotatable tool holder and the stationary support member, a centrifugal force acts on the cutting fluid, flowing in a direction conforming to the direction of rotation of the tool holder, in a direction counter to the direction of flow of the cutting fluid. Therefore, this conventional method has an additional disadvantage in that the pressure of the cutting fluid being poured onto the workpiece is considerably reduced.